Several projects in adjuvants and vaccine delivery systems have been undertaken:The separation of several pure compounds from commercially available Saponin from Quillaja bark has been performed (QS-7, QS-18, QS- 21). The exact structure of these powerful adjuvants is still unknown. An investigation as to the exact composition/structure of the compounds in solution and how that affects their interaction with peptides (i.e. antigens) in general and with possible target cells in the immune system will be undertaken. Furthermore a comparison of the structure of potent adjuvants with little hemolytic activity such as QS21 and those which are potent adjuvants but highly toxic such as QS18 will help us understand which structural properties contribute to adjuvanticity and which to toxicity. An investigation into the use of polysaccharide microspheres as a possible vaccine delivery system has been started. Microencapsulating with polysaccharides offers several advantages over materials which are presently being investigated in microencapsulating antigens. First, the encapsulation is done in absence of organic solvents avoiding possible denaturing of antigens and traces of unacceptable chemical in the final product. Second, it is less likely that the environment inside the capsule will become unfavorable to the antigen creating stability problems. Furthermore, a study will be carried out to examine if the polysaccharide capsule it-self could be an antigen for a T-dependent immune response to bacterial capsule polysaccharides when these are used to encapsulate an immunogenic protein.